1. Field of the Invention
The present invention relates to an alternating current generator with an improved fan system, and more particularly, to an alternating current generator in which a rotor is provided with fans for producing cooling air.
The instant application claims priority from Japanese Patent Application No. HEI 7-287289, filed Nov. 6, 1995, which is incorporated herein by reference for all purposes.
2. Description of Related Art
U.S. Pat. No. 4,492,885 discloses a conventional alternating current generator in which a rotor is provided with fans to produce cooling air for cooling the alternating current generator itself.
One of the conventional alternating current generators is hereinafter discussed.
FIG. 15 is a sectional view showing the conventional alternating current generator for a car. FIG. 16 is a perspective view showing a rotor of the generator. FIG. 17 is a partial perspective view showing a fan (ventilating portion) 14 which is attached to the rotor.
As shown, the alternator includes a rotor 1, a rotary shaft 11 driven by a driving force transmitted from an internal combustion engine of a car (not shown) by way of a belt (not shown), a pair of Rondel-type field cores 12, and a field winding 13. The alternator further includes a stator 2 having a stator core 21 and a stator winding 22 which faces the rotor 1 at a predetermined distance therefrom. A front bracket 3 and a rear bracket 4, rotatably support the rotor 1 through bearings 31, 41 and securely hold the stator 2 therebetween. Fans 14, 15 are fixed to the Rondel-type field core 12. Blades 14a, 15a are formed by cut-raising the fans 14, 15.
The Rondel-type field cores 12 are formed into a Rondel-shape as shown in FIG. 15 by the steps of forming a low carbon steel or the like into a star shape by forging, etc. and bend-raising a nail portion 12b projecting from a core portion 12a. 
With regard to the operation of the conventional alternating current generator of the above-construction, when the rotor 1 is rotated by an external driving force, a magnetic field generated by the field winding 13 surrounds the Rondel-type field cores 12, and the magnetic field passes through the stator winding 22 in conformity with the rotation of the rotor 1, whereby a current is generated on the stator winding 22 and power is generated through a rectifier 5.
Furthermore, when the rotor 1 is rotated, the fans 14 and 15 fixed to the side of the Rondel-type field cores 12 are also rotated, and the blades 14a, 15a revolve, whereby air flow takes place inside the generator. The air flows may be principally divided into: (1) flows (a) and (b) flowing in through an inlet port 3a of the front bracket, passing through the coil end of the stator winding 22, and flowing out through an outlet port 3b of the front bracket, and (2) flows (c) and (d) flowing in through an inlet port 4a of the rear bracket, passing through the rectifier 5 and brush 6, and flowing out through an outlet port 4b of the rear bracket. The inside of the generator is cooled by the air flows.
In the conventional battery charging alternating current generator of the above-mentioned construction and operation, a problem exists in that the space inside the battery charging alternating current generator is limited, making it impossible to enlarge the area of the blades 14a, 15a of the fans 14, 15 and thus improve cooling efficiency, thus resulting in a temperature rise occurring inside the generator. In particular, the surroundings of the stator 2 which generate heat during the power generation, are not sufficiently cooled.
Japanese Laid-Open Patent Publication (unexamined) No.1943, 651/1984 discloses an alternating current generator in which a fan is bent to be closely and securely fixed to a core. A problem, however, exists in that since the entire fan is bent along the core, a rather complicated shape and assembly process are required. Moreover, the shape of the blades may be disadvantageously deformed.
The object of the present invention is to solve the above-discussed problems by providing an alternating current generator having improved cooling efficiency, whose method of manufacture is easier.
Another object of the invention is to provide fans for use in an alternating current generator which are easy to manufacture, can be easily mounted on the alternating current generator, and are capable of improving the cooling efficiency of the alternating current generator.
An alternating current generator in accordance with the invention comprises: (1) a rotor having a rotary shaft and a field winding, which is rotated by transmission of a driving force; (2) a bracket for holding the rotor rotatably; (3) a stator fixed to the bracket, having a stationary core and a stationary winding; (4) fans fixed to the rotor; (5) blades formed directly from the fans in the direction toward the bracket; and (6) protruding portions formed directly from the blades in the direction toward the rotor. Consequently, the fans, blades thereof, and protruding portions may be formed easily by press working, and cooling efficiency may be improved.
It is preferable that the blades and projecting portions of the alternating current generator are formed by cut-raising and that the protruding portions are formed into a shape in line with the shape of the rotor. Consequently, a gap between the rotor and each protruding portion may be reduced and the area of the protruding portions may be enlarged as much, resulting in improvement of cooling efficiency.
It is also preferable that the blades be formed by cut-raising the fans toward the bracket side, with each blade being provided with a plate fixed to an end of that blade and a projecting part being mounted on the end of each blade for the positioning of the plate. Consequently, the plates may be easily mounted, and the cooling efficiency may be improved as a result of rectification effect and increase in area by the projecting parts.
It is also preferable that the blades be formed by cut-raising the fans toward the bracket and each blade is provided with a plate portion formed by bending an end portion of the blade. Consequently, the plate portions may be formed simultaneously at the time of press working of the fans, resulting in easy manufacturing.
Another embodiment of an alternating current generator in accordance with the invention comprises: (1) a rotor having a rotary shaft and a field winding, which is rotated by transmission of a driving force; (2) a bracket for holding the rotor rotatably; (3) a stator fixed to the bracket, having a stationary core and a stationary winding; (4) fans fixed to the rotor; (5) blades formed rotatably on the fans; and (6) protruding portions formed on the blades into a shape that is in line with the rotor. Consequently, a sufficient air flow rate is obtained during revolution at a low speed and a reduction of noise is achieved during revolution at a high speed as a result of forming the rotatable fans. Furthermore, cooling performance may be improved as a result of forming the protruding portions.
It is also preferable that in the alternating current generator in accordance with the invention the blades directed toward the bracket are formed by cut-raising, and that the protruding portions are formed in the opposite direction of the bracket by simultaneously cut-raising them when cut-raising the blades directed to the bracket. Consequently, the inventive fans of improved cooling efficiency may be easily manufactured by a press working operation.
The other objects and features of this invention will be understood from the following description with reference to the accompanying drawings.